build: fix linking of opensc-notify.exe on Windows

[H5117]

With Visual Studio 2022 I get:

FAILED: src/tools/opensc-notify.exe src/tools/opensc-notify.pdb
"link"  /MACHINE:x64 /OUT:src/tools/opensc-notify.exe src/tools/src_tools_versioninfo-opensc-notify.rc_versioninfo-opensc-notify.res src/tools/opensc-notify.exe.p/meson-generated_.._opensc-notify-cmdline.c.obj src/tools/opensc-notify.exe.p/opensc-notify.c.obj "/release" "/nologo" "/DEBUG" "/PDB:src/tools\opensc-notify.pdb" "src/common/libcompat.a" "src/libopensc/libopensc.a" "src/common/libscdl.a" "src/scconf/libscconf.a" "src/ui/libstrings.a" "src/ui/libnotify.a" "src/pkcs15init/libpkcs15init.a" "src/sm/libsmeac.a" "src/sm/libsmiso.a" "winscard.lib" "/SUBSYSTEM:CONSOLE" "advapi32.lib" "comctl32.lib" "gdi32.lib" "shell32.lib" "shlwapi.lib" "user32.lib" "ws2_32.lib"
libnotify.a(notify.c.obj) : error LNK2005: create_invisible_window already defined in opensc-notify.c.obj
libnotify.a(notify.c.obj) : error LNK2005: WndProc already defined in opensc-notify.c.obj
src\tools\opensc-notify.exe : fatal error LNK1169: one or more multiply defined symbols found